This invention relates to hand operated swimming aids and more particularly to paddles with movable flaps and vertical stabilizers for use with the paddles.
U.S. Pat. No. 5,348,503 issued Sep. 20, 1994 to the applicant discloses a paddle with a blade at opposite ends of a hand held shaft. Each blade has a rigid leading edge and a flexible following portion. When pushed forward, the blade lies in a plane for minimal resistance. When pulled backward on the power stroke, the following portion bends out of the plane, creating increased resistance for enhanced propulsion. This pulling action causes torso and legs to move from side to side, reducing the forward power thrust. A vertical blade held on both feet acts as a keel or stabilizer to reduce the lateral motion and convert it to forward thrust.
Canadian Patent No. 757954 issued May 1967 discloses a double ended swimmer's paddle with hinged flaps. The flaps are supposed to open on the power stroke, with cords 19 limiting the extent of opening, to create high resistance, and to close on the return stroke for low resistance. If the angle of attack is not directed between the flaps, the flaps will move in the same direction, reducing their utility. On the power stroke the flaps tend to vibrate, increasing resistance without adding thrust.
U.S. Pat. No. 2,948,255 issued Aug. 9, 1960 to Sbrana discloses resilient paired flaps that reciprocate on a paddle mechanism mounted beneath a water craft.
U.S. Pat. No. 5,362,268 issued Nov. 8, 1994 to Nordbeck discloses a foot mounted swim fin. The fin has resilient side panels which tend to bend toward one another on the return stroke.
U.S. Pat. No. 3,510,894 issued May 12, 1970 to Eriksen and U.S. Pat. No. 5,114,371 issued May 19, 1992 to Alonzo disclose a floating double ended paddle that buoys the swimmer and provides propulsion, the paddle ends are rigid.
U.S. Pat. No. 3,987,509 issued Oct. 26, 1976 to Patterman discloses a swimming tail formed by a pair of flippers to be used side by side to simulate the vertical tail of a fish, one flipper has a fin that extends back from the heel of the foot and the other has a fin that extends forward from the toe of the foot. Thrust is generated by lateral motion of the pair.
U.S. Pat. No. 4,857,024 issued Aug. 15, 1989 to Evans teaches a swim fin mounted on the foot with a shaped, horizontal blade having special flexing responses that are greater when forced through the water in a first direction than in a second direction so that greater resistance is offered on the power stroke of the kick and less on the return stroke. The propelling force is developed by a combination of the flexing of the deflectable end and the snapping action of the movable tips.
The prior art does not consider the problems related to flaps not opening correctly when the angle of attack changes nor to vibration of the flaps.